minix/lib/libsffs/inode.c

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/* This file deals with inode management.
*
* The entry points into this file are:
* init_inode initialize the inode table, return the root inode
* find_inode find an inode based on its inode number
* get_inode increase the reference count of an inode
* put_inode decrease the reference count of an inode
* link_inode link an inode as a directory entry to another inode
* unlink_inode unlink an inode from its parent directory
* get_free_inode return a free inode object
* have_free_inode check whether there is a free inode available
* have_used_inode check whether any inode is still in use
* do_putnode perform the PUTNODE file system call
*
* Created:
* April 2009 (D.C. van Moolenbroek)
*/
#include "inc.h"
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static struct inode inodes[NUM_INODES];
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static TAILQ_HEAD(free_head, inode) free_list;
/*===========================================================================*
* init_inode *
*===========================================================================*/
struct inode *init_inode(void)
{
/* Initialize inode table. Return the root inode.
*/
struct inode *ino;
unsigned int index;
TAILQ_INIT(&free_list);
dprintf(("%s: %d inodes, %u bytes each, equals %u bytes\n",
sffs_name, NUM_INODES, sizeof(struct inode), sizeof(inodes)));
/* Mark all inodes except the root inode as free. */
for (index = 1; index < NUM_INODES; index++) {
ino = &inodes[index];
ino->i_parent = NULL;
LIST_INIT(&ino->i_child);
ino->i_num = index + 1;
ino->i_gen = (unsigned short)-1; /* aesthetics */
ino->i_ref = 0;
ino->i_flags = 0;
TAILQ_INSERT_TAIL(&free_list, ino, i_free);
}
/* Initialize and return the root inode. */
ino = &inodes[0];
ino->i_parent = ino; /* root inode is its own parent */
LIST_INIT(&ino->i_child);
ino->i_num = ROOT_INODE_NR;
ino->i_gen = 0; /* unused by root node */
ino->i_ref = 1; /* root inode is hereby in use */
ino->i_flags = I_DIR; /* root inode is a directory */
ino->i_name[0] = 0; /* root inode has empty name */
return ino;
}
/*===========================================================================*
* find_inode *
*===========================================================================*/
struct inode *find_inode(pino_t ino_nr)
{
/* Get an inode based on its inode number. Do not increase its reference count.
*/
struct inode *ino;
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int index;
/* Inode 0 (= index -1) is not a valid inode number. */
index = INODE_INDEX(ino_nr);
if (index < 0) {
printf("%s: VFS passed invalid inode number!\n", sffs_name);
return NULL;
}
assert(index < NUM_INODES);
ino = &inodes[index];
/* Make sure the generation number matches. */
if (INODE_GEN(ino_nr) != ino->i_gen) {
printf("%s: VFS passed outdated inode number!\n", sffs_name);
return NULL;
}
/* The VFS/FS protocol only uses referenced inodes. */
if (ino->i_ref == 0)
printf("%s: VFS passed unused inode!\n", sffs_name);
return ino;
}
/*===========================================================================*
* get_inode *
*===========================================================================*/
void get_inode(struct inode *ino)
{
/* Increase the given inode's reference count. If both reference and link
* count were zero before, remove the inode from the free list.
*/
dprintf(("%s: get_inode(%p) ['%s']\n", sffs_name, ino, ino->i_name));
/* (INUSE, CACHED) -> INUSE */
/* If this is the first reference, remove the node from the free list. */
if (ino->i_ref == 0 && !HAS_CHILDREN(ino))
TAILQ_REMOVE(&free_list, ino, i_free);
ino->i_ref++;
if (ino->i_ref == 0)
panic("inode reference count wrapped");
}
/*===========================================================================*
* put_inode *
*===========================================================================*/
void put_inode(struct inode *ino)
{
/* Decrease an inode's reference count. If this count has reached zero, close
* the inode's file handle, if any. If both reference and link count have
* reached zero, mark the inode as cached or free.
*/
dprintf(("%s: put_inode(%p) ['%s']\n", sffs_name, ino, ino->i_name));
assert(ino != NULL);
assert(ino->i_ref > 0);
ino->i_ref--;
/* If there are still references to this inode, we're done here. */
if (ino->i_ref > 0)
return;
/* Close any file handle associated with this inode. */
put_handle(ino);
/* Only add the inode to the free list if there are also no links to it. */
if (HAS_CHILDREN(ino))
return;
/* INUSE -> CACHED, DELETED -> FREE */
/* Add the inode to the head or tail of the free list, depending on whether
* it is also deleted (and therefore can never be reused as is).
*/
if (ino->i_parent == NULL)
TAILQ_INSERT_HEAD(&free_list, ino, i_free);
else
TAILQ_INSERT_TAIL(&free_list, ino, i_free);
}
/*===========================================================================*
* link_inode *
*===========================================================================*/
void link_inode(struct inode *parent, struct inode *ino)
{
/* Link an inode to a parent. If both reference and link count were zero
* before, remove the inode from the free list. This function should only be
* called from add_dentry().
*/
/* This can never happen, right? */
if (parent->i_ref == 0 && !HAS_CHILDREN(parent))
TAILQ_REMOVE(&free_list, parent, i_free);
LIST_INSERT_HEAD(&parent->i_child, ino, i_next);
ino->i_parent = parent;
}
/*===========================================================================*
* unlink_inode *
*===========================================================================*/
void unlink_inode(struct inode *ino)
{
/* Unlink an inode from its parent. If both reference and link count have
* reached zero, mark the inode as cached or free. This function should only
* be used from del_dentry().
*/
struct inode *parent;
parent = ino->i_parent;
LIST_REMOVE(ino, i_next);
if (parent->i_ref == 0 && !HAS_CHILDREN(parent)) {
if (parent->i_parent == NULL)
TAILQ_INSERT_HEAD(&free_list, parent, i_free);
else
TAILQ_INSERT_TAIL(&free_list, parent, i_free);
}
ino->i_parent = NULL;
}
/*===========================================================================*
* get_free_inode *
*===========================================================================*/
struct inode *get_free_inode(void)
{
/* Return a free inode object (with reference count 1), if available.
*/
struct inode *ino;
/* [CACHED -> FREE,] FREE -> DELETED */
/* If there are no inodes on the free list, we cannot satisfy the request. */
if (TAILQ_EMPTY(&free_list)) {
printf("%s: out of inodes!\n", sffs_name);
return NULL;
}
ino = TAILQ_FIRST(&free_list);
TAILQ_REMOVE(&free_list, ino, i_free);
assert(ino->i_ref == 0);
assert(!HAS_CHILDREN(ino));
/* If this was a cached inode, free it first. */
if (ino->i_parent != NULL)
del_dentry(ino);
assert(ino->i_parent == NULL);
/* Initialize a subset of its fields */
ino->i_gen++;
ino->i_ref = 1;
return ino;
}
/*===========================================================================*
* have_free_inode *
*===========================================================================*/
int have_free_inode(void)
{
/* Check whether there are any free inodes at the moment. Kind of lame, but
* this allows for easier error recovery in some places.
*/
return !TAILQ_EMPTY(&free_list);
}
/*===========================================================================*
* have_used_inode *
*===========================================================================*/
int have_used_inode(void)
{
/* Check whether any inodes are still in use, that is, any of the inodes have
* a reference count larger than zero.
*/
unsigned int index;
for (index = 0; index < NUM_INODES; index++)
if (inodes[index].i_ref > 0)
return TRUE;
return FALSE;
}
/*===========================================================================*
* do_putnode *
*===========================================================================*/
int do_putnode(void)
{
/* Decrease an inode's reference count.
*/
struct inode *ino;
int count;
if ((ino = find_inode(m_in.REQ_INODE_NR)) == NULL)
return EINVAL;
count = m_in.REQ_COUNT;
if (count <= 0 || count > ino->i_ref) return EINVAL;
ino->i_ref -= count - 1;
put_inode(ino);
return OK;
}